Day 8. I wonder if this wouldn't have been a good excuse to find a Rust/SMT binding.

Cargo.lock

@@ -6,9 +6,25 @@ version = 3
 name = "advent2021"
 version = "0.1.0"
 dependencies = [
+ "itertools",
  "thiserror",
 ]
 
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
+[[package]]
+name = "itertools"
+version = "0.10.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a9a9d19fa1e79b6215ff29b9d6880b706147f16e9b1dbb1e4e5947b5b02bc5e3"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "proc-macro2"
 version = "1.0.32"

Cargo.toml

@@ -4,4 +4,5 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
+itertools = "0.10.3"
 thiserror = "1.0"

data/day8a.txt

@@ -0,0 +1,200 @@
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+fcbegda dbcefg gcebad gbfc cdb gfbaed bc cebfd ecdfa bdegf | dcb gabedf beafdg bc
+cfaed bacdg egd aegcdf gcef gedac cdbefga afdgbe bdfaec eg | gcade cefad bdgfea gaedc
+ac dbeacg ace defba fcaebdg dabfce abfedg dcaf cbfae efbcg | fegdba cfbae cea dbacfe
+dgcaef bgcaef cfdgeb gd fgecb dcgfbae gebfd bgdc adebf fdg | gdf dafgbec dfg adfeb
+ag cadg cgfed aefbc bcegdf agdfbe agf egfca gefcdba gdfeac | dgca dgcaef cdga adebcfg
+dfcgbe badg aedgc eabfc dfcbega cgdafe eagbc aegcdb gbe bg | acfdge bge adbg bg
+bcfage adcefg dfagc fgaec cdf abcgd dcbgafe df dfae fgcbed | df cfd eacgf fdc
+cbadfe bfg cfgebd cbdg edfgbca bg egbdf feagcb fedag cefdb | fgdeb gfb fbdeca bgcd
+bcde fdcgba abfcde dbfac abefc befga aec ce acfdge afdegbc | fcbad eac ec becd
+ce cbagdf gdcbf cfaebdg gcbe acfdge fcdegb dbaef cef bcefd | acbgdfe cfebd gcebdf ec
+ecgbd eacbf cgadeb edf ecafbdg afgebd dcgf ecfbd fgcbed fd | bcfea edf efgabcd df
+dgbf egafcd cfedbag cgb abcef dcefg ebcfg cgeadb bg cgbfed | adfgebc egbcf cfeab gaefbdc
+gecbfd gbedc dgabcef baefgd abegc dbfce bfdace dg gdb dfcg | dfgc bedfac dg dbg
+acbdgf daeb gcbeaf gdfce adefg fbdga cbdfega fae fgdbea ea | ea fcdgaeb ae gecfadb
+ga bdgafe bcaed dcgaebf bacfed acedg gbadec edgfc agd bcga | adg dga agcb fdecgab
+ebdcfg cfbdg ecgabf gcd edfc fdcbeag ebcdag dabgf dc cgebf | cd gcd gacbde cd
+egdfac bf afebdg baf bfdeca bgdf fedga egacb gecbafd gbeaf | bfa fb gfdb fb
+gcafb dc gecd fecbgda cfdbg dfebgc cdf fbegd dcfbea fgedab | edfcbg dgbcf cd dcf
+badf fcagd agcefb dfgcab ba dcbeg cedabgf abgdc acegfd abg | ebfagc dfab ab fcbdeag
+cfgbad gdbfe fe efgdacb cbdge dabgfe egdcaf befa bdgfa egf | decagfb eabf baef fe
+dbfea bcaefdg dcfgeb ag bfceag egfcda becfg fgeba gcab ega | agbfecd aedfcgb gcba ga

data/day8t.txt

@@ -0,0 +1,10 @@
+be cfbegad cbdgef fgaecd cgeb fdcge agebfd fecdb fabcd edb | fdgacbe cefdb cefbgd gcbe
+edbfga begcd cbg gc gcadebf fbgde acbgfd abcde gfcbed gfec | fcgedb cgb dgebacf gc
+fgaebd cg bdaec gdafb agbcfd gdcbef bgcad gfac gcb cdgabef | cg cg fdcagb cbg
+fbegcd cbd adcefb dageb afcb bc aefdc ecdab fgdeca fcdbega | efabcd cedba gadfec cb
+aecbfdg fbg gf bafeg dbefa fcge gcbea fcaegb dgceab fcbdga | gecf egdcabf bgf bfgea
+fgeab ca afcebg bdacfeg cfaedg gcfdb baec bfadeg bafgc acf | gebdcfa ecba ca fadegcb
+dbcfg fgd bdegcaf fgec aegbdf ecdfab fbedc dacgb gdcebf gf | cefg dcbef fcge gbcadfe
+bdfegc cbegaf gecbf dfcage bdacg ed bedf ced adcbefg gebcd | ed bcgafe cdgba cbgef
+egadfb cdbfeg cegd fecab cgb gbdefca cg fgcdab egfdb bfceg | gbdfcae bgc cg cgb
+gcafb gcf dcaebfg ecagb gf abcdeg gaef cafbge fdbac fegbdc | fgae cfgab fg bagce

src/bin/day8.rs

@@ -0,0 +1,312 @@
+use itertools::Itertools;
+use std::collections::{HashMap, HashSet};
+
+#[cfg(test)]
+const TEST_DATA: &str = include_str!("../../data/day8t.txt");
+const DAY8_DATA: &str = include_str!("../../data/day8a.txt");
+
+#[derive(Clone)]
+struct ProblemInput<'a> {
+    signal_patterns: [&'a str; 10],
+    output_values: [&'a str; 4],
+}
+
+impl<'a> From<&'a str> for ProblemInput<'a> {
+    fn from(x: &'a str) -> Self {
+        let (signals, outputs) = x.split_once(" | ").unwrap();
+        let mut signal_patterns = [""; 10];
+        let mut output_values = [""; 4];
+
+        for (i, val) in signals.split(' ').enumerate() {
+            signal_patterns[i] = val;
+        }
+
+        for (i, val) in outputs.split(' ').enumerate() {
+            output_values[i] = val;
+        }
+
+        ProblemInput {
+            signal_patterns,
+            output_values,
+        }
+    }
+}
+
+#[test]
+fn problem_input() {
+    let input =
+        "acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab | cdfeb fcadb cdfeb cdbaf";
+    let parsed = ProblemInput::from(input);
+    assert_eq!(
+        ["acedgfb", "cdfbe", "gcdfa", "fbcad", "dab", "cefabd", "cdfgeb", "eafb", "cagedb", "ab"],
+        parsed.signal_patterns
+    );
+    assert_eq!(["cdfeb", "fcadb", "cdfeb", "cdbaf"], parsed.output_values);
+}
+
+fn from_file_data(input_file: &str) -> Vec<ProblemInput<'_>> {
+    let mut retval = Vec::new();
+
+    for line in input_file.lines() {
+        retval.push(ProblemInput::from(line));
+    }
+
+    retval
+}
+
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
+enum Segment {
+    Top,
+    TopLeft,
+    TopRight,
+    Middle,
+    BottomLeft,
+    BottomRight,
+    Bottom,
+}
+
+const SEGMENTS_USED: [&[Segment]; 10] = [
+    /* 0 */
+    &[
+        Segment::Top,
+        Segment::TopLeft,
+        Segment::TopRight,
+        Segment::BottomLeft,
+        Segment::BottomRight,
+        Segment::Bottom,
+    ],
+    /* 1 */ &[Segment::TopRight, Segment::BottomRight],
+    /* 2 */
+    &[
+        Segment::Top,
+        Segment::TopRight,
+        Segment::Middle,
+        Segment::BottomLeft,
+        Segment::Bottom,
+    ],
+    /* 3 */
+    &[
+        Segment::Top,
+        Segment::TopRight,
+        Segment::Middle,
+        Segment::BottomRight,
+        Segment::Bottom,
+    ],
+    /* 4 */
+    &[
+        Segment::TopLeft,
+        Segment::TopRight,
+        Segment::Middle,
+        Segment::BottomRight,
+    ],
+    /* 5 */
+    &[
+        Segment::Top,
+        Segment::TopLeft,
+        Segment::Middle,
+        Segment::BottomRight,
+        Segment::Bottom,
+    ],
+    /* 6 */
+    &[
+        Segment::Top,
+        Segment::TopLeft,
+        Segment::Middle,
+        Segment::BottomRight,
+        Segment::BottomLeft,
+        Segment::Bottom,
+    ],
+    /* 7 */ &[Segment::Top, Segment::TopRight, Segment::BottomRight],
+    /* 8 */
+    &[
+        Segment::Top,
+        Segment::TopLeft,
+        Segment::TopRight,
+        Segment::Middle,
+        Segment::BottomLeft,
+        Segment::BottomRight,
+        Segment::Bottom,
+    ],
+    /* 9 */
+    &[
+        Segment::Top,
+        Segment::TopLeft,
+        Segment::TopRight,
+        Segment::Middle,
+        Segment::BottomRight,
+        Segment::Bottom,
+    ],
+];
+
+fn recognize_number(segs: &[Segment]) -> Option<usize> {
+    for (result, digit_info) in SEGMENTS_USED.iter().enumerate() {
+        if digit_info.len() == segs.len() && segs.iter().all(|x| digit_info.contains(x)) {
+            return Some(result);
+        }
+    }
+
+    None
+}
+
+fn reasonable_assignments(assigns: &HashMap<char, Segment>) -> bool {
+    let mut tester = HashSet::new();
+
+    for value in assigns.values() {
+        if tester.contains(value) {
+            return false;
+        }
+        tester.insert(value);
+    }
+
+    true
+}
+
+fn build_local_iterator<'a>(
+    input: (&'a char, &'a HashSet<Segment>),
+) -> impl Iterator<Item = (char, Segment)> + Clone + 'a {
+    let (c, set) = input;
+    set.iter().map(|x| (*c, *x))
+}
+
+impl<'a> ProblemInput<'a> {
+    fn unique_outputs(&self) -> usize {
+        let mut result = 0;
+
+        for v in self.output_values.iter() {
+            let len = v.len();
+
+            if len == 2 || len == 4 || len == 3 || len == 7 {
+                result += 1;
+            }
+        }
+
+        result
+    }
+
+    fn find_letters_for(&self, len: usize) -> &str {
+        for x in self.signal_patterns {
+            if x.len() == len {
+                return x;
+            }
+        }
+        panic!("Couldn't find letters for size {}", len);
+    }
+
+    fn possible_assignments(&self) -> HashMap<char, HashSet<Segment>> {
+        let mut result = HashMap::new();
+
+        for label in 'a'..='g' {
+            result.insert(label, SEGMENTS_USED[8].iter().copied().collect());
+        }
+
+        let one = self.find_letters_for(2);
+        let four = self.find_letters_for(4);
+        let seven = self.find_letters_for(3);
+
+        for letter in one.chars() {
+            result.insert(
+                letter,
+                HashSet::from([Segment::TopRight, Segment::BottomRight]),
+            );
+        }
+
+        for letter in four.chars() {
+            if !one.contains(letter) {
+                result.insert(letter, HashSet::from([Segment::TopLeft, Segment::Middle]));
+            }
+        }
+
+        for letter in seven.chars() {
+            if !one.contains(letter) {
+                result.insert(letter, HashSet::from([Segment::Top]));
+            }
+        }
+
+        result
+    }
+
+    fn assignments_validate(&self, assignments: &HashMap<char, Segment>) -> bool {
+        let mut found = HashSet::new();
+
+        for input in self.signal_patterns {
+            let segments: Vec<Segment> = input
+                .chars()
+                .map(|x| assignments.get(&x).unwrap())
+                .copied()
+                .collect();
+            match recognize_number(&segments) {
+                None => return false,
+                Some(x) if found.contains(&x) => return false,
+                Some(x) => {
+                    found.insert(x);
+                }
+            }
+        }
+
+        true
+    }
+
+    fn compute_output(&self, assignments: HashMap<char, Segment>) -> Option<usize> {
+        let mut result = 0;
+
+        for output in self.output_values.iter() {
+            let segments: Vec<Segment> = output
+                .chars()
+                .map(|x| assignments.get(&x).unwrap())
+                .copied()
+                .collect();
+            let value = recognize_number(&segments)?;
+            result = (result * 10) + value;
+        }
+
+        Some(result)
+    }
+
+    fn solve(&self) -> Option<usize> {
+        let possible_sets = self.possible_assignments();
+        let possibles = possible_sets
+            .iter()
+            .map(build_local_iterator)
+            .multi_cartesian_product()
+            .map(|x| HashMap::from_iter(x.iter().cloned()))
+            .filter(|x| reasonable_assignments(x));
+
+        for assignments in possibles {
+            if self.assignments_validate(&assignments) {
+                if let Some(result) = self.compute_output(assignments) {
+                    return Some(result);
+                }
+            }
+        }
+
+        None
+    }
+}
+
+fn count_unique_outputs(inputs: &[ProblemInput]) -> usize {
+    inputs.iter().map(|x| x.unique_outputs()).sum()
+}
+
+fn sum_outputs(inputs: &[ProblemInput]) -> usize {
+    inputs.iter().map(|x| x.solve().unwrap()).sum()
+}
+
+#[test]
+fn regression() {
+    let example_input =
+        "acedgfb cdfbe gcdfa fbcad dab cefabd cdfgeb eafb cagedb ab | cdfeb fcadb cdfeb cdbaf";
+    let example = ProblemInput::from(example_input);
+    assert_eq!(5353, sum_outputs(&[example]));
+
+    let test_data = from_file_data(TEST_DATA);
+    assert_eq!(26, count_unique_outputs(&test_data));
+    assert_eq!(61229, sum_outputs(&test_data));
+    let real_data = from_file_data(DAY8_DATA);
+    assert_eq!(519, count_unique_outputs(&real_data));
+}
+
+fn main() {
+    let real_data = from_file_data(DAY8_DATA);
+    println!("Part #1: {}", count_unique_outputs(&real_data));
+    println!("Part #2: {}", sum_outputs(&real_data));
+}